66 



PAUL J. ANDERSON 



phthalein, nor does it seem to be toxic to the apple pollen. In fact 

 apple pollen germinates in tap water which contains a relatively 

 large amount of calcimxi almost as well a,s it does in distilled 

 water. 



Raspberry. This was not the case with the raspberry pollen 

 which was next used. When the solutions for this experiment 

 were made with tap water, 18% germination of the grains was 

 secured, while with distilled water 83% germinated. The germ 

 tubes in the former were not as long nor as \'igorous. Tests of 

 this same pollen were made in the water after the calcium had 

 been crystallized out as previously, but here the germination 

 was reduced to 11%; this shows quite a different result from that 

 obtained with the apple pollen. In this case the calcium is evi- 

 dently toxic whether in the caustic condition or not. 



The raspberry pollen experiments were to determine two points : 

 (1) How weak a solution of the cement dust will prevent ger- 

 mination? (2) How weak a solution of calcium oxide will pre- 

 vent germination? Raspberry pollen germinated very readily 

 in 30% saccharose. No check gave less than 90% germination. 

 Solutions of the cement dust were made up 1-500, 1-700, 1-800, 

 1-1000, 1-1200, 1-1500, 1-1600, 1-1800, and 1-2000. After fil- 

 tration these were used to make 30% saccharose solutions. Up 

 to 1-1500 there was no germination except for an occasional 

 short tube. Above this, slight germination occurred, reaching 

 6% in the 1-2000 solution. But even here the tubes were rarely 

 more than four times as long as the diameter of the grain, while 

 in the checks in the same period of tune, they were thirty times 

 the diameter of the grain. The results of the second series is 

 given in the following table. 



TABLE VII 



Shoivs the comparative qermination of red raspberry -pollen in different concentra- 

 tions of the cement dust solution 



